As described in numerous published patent applications, a system has been developed for cleaning particles from a semiconductor wafer with a high viscosity, non-Newtonian fluid deposited at a low velocity. See e.g., U.S. Published Patent Application No. 2006/0283486 entitled “Method and Apparatus for Cleaning a Substrate Using Non-Newtonian Fluids,” filed on Jun. 15, 2005, U.S. Published Patent Application No. 2006/0128590 entitled “Method for Removing Contamination from a Substrate and for Making a Cleaning Solution,” filed on Feb. 3, 2006, and U.S. Published Patent Application No. 2006/0128600 entitled “Cleaning Compound and Method and System for Using the Cleaning Compound,” filed on Feb. 3, 2006, all of which are hereby incorporated by reference.
In particular implementations, the high viscosity, non-Newtonian fluid is a foam created by mechanically mixing a gas (such as nitrogen) and a fluid (an aqueous solution with a surfactant such as a fatty acid capable of forming micelles) in the microchannels formed by a packet of thousands of sapphire beads (e.g., approximately 1 mm in diameter).
There are considerable drawbacks to such implementations. Sapphire beads are relatively expensive and react with the foam. Moreover, bead packets tend to clog fairly frequently and take considerable time and expense to clean.
As a result of these drawbacks, there is a need to provide an inexpensive, readily maintainable apparatus, method, and system for mechanically generating a foam to clean a substrate (e.g., a semiconductor wafer).